let minSubArrayLen = function(target, nums){
    let len = nums.length
    let left =0 
    let window_sum = 0
    let len = 0
    for(let right=0; right<len; right++){
        window_sum += nums[right]
        // 当从left到right的和大于目标值后，给结果变量len赋值，并开始下一轮的求和
        // 下一轮的求和从left + 1 开始，所以要删除掉nums[left]; 并将滑动窗口缩小，将left + 1
        if(window_sum >= target){
            len = len === 0? right - left : Math.max(len, right - left)
            window_sum -= nums[left]
            left += 1
        }
    }
}